HIV is a retrovirus that targets CD4+ T-lymphocytes, the immune cells that coordinate defense against infection. Untreated, HIV destroys CD4 cells over years and progresses to AIDS when the count falls below 200 cells/µL or an AIDS-defining illness develops.
HIV/AIDS (ICD-10: B20 for symptomatic HIV disease, Z21 for asymptomatic HIV infection status) is a chronic, progressive infection caused by the human immunodeficiency virus, a single-stranded RNA retrovirus of the genus Lentivirus. Two species infect humans: HIV-1 accounts for nearly all global infections, while HIV-2 is largely confined to West Africa and progresses more slowly. The virus binds CD4 receptors and CCR5 or CXCR4 co-receptors on T-helper lymphocytes, monocytes, and dendritic cells; reverse transcriptase converts viral RNA to DNA, which integrates into the host genome as a permanent reservoir. Without antiretroviral therapy, ongoing viral replication depletes CD4+ T cells at roughly 50-100 cells/µL per year, producing the clinical syndrome of acquired immunodeficiency syndrome (AIDS) once the count drops below 200 cells/µL or an AIDS-defining opportunistic infection or malignancy occurs.
The key symptoms of HIV/AIDS are: Acute retroviral syndrome 2-4 weeks after exposure: fever, fatigue, sore throat, swollen cervical and axillary lymph nodes, and a maculopapular trunk rash lasting 1-3 weeks in 40-90% of newly infected adults., Persistent generalized lymphadenopathy — painless rubbery nodes larger than 1 cm at two or more non-contiguous sites lasting more than 3 months, often the first physical sign during clinical latency., Unexplained weight loss of more than 10% of body weight, often accompanied by chronic diarrhea lasting more than a month, signaling advancing immunodeficiency., Recurrent oral or esophageal candidiasis (thrush): white removable plaques on the tongue, palate, or buccal mucosa; odynophagia and retrosternal pain when the esophagus is involved., Recurrent or multi-dermatomal shingles (herpes zoster), particularly in adults under 50 — a herald of HIV in many resource-limited settings., Chronic dry cough, exertional dyspnea, and low-grade fever suggesting Pneumocystis jirovecii pneumonia once CD4 falls below 200 cells/µL., Night sweats severe enough to soak bedding, often paired with low-grade fever and progressive fatigue..
Diagnosis of HIV follows a tiered testing algorithm endorsed by the CDC and WHO. First-line screening is a fourth-generation laboratory antigen/antibody combination immunoassay that detects both HIV-1/2 antibodies and the p24 capsid antigen, shortening the diagnostic window to about 2-4 weeks after infection. A reactive screen is followed by an HIV-1/HIV-2 antibody differentiation immunoassay to confirm seropositivity and distinguish the two species. Discordant results — reactive screen but negative differentiation — trigger HIV-1 RNA nucleic acid testing to detect acute infection before antibodies develop. In low-resource and community testing settings, rapid diagnostic tests using finger-stick blood or oral fluid provide same-visit results; WHO recommends a three-test algorithm for confirmed diagnosis where laboratory access is limited. HIV self-tests are now approved in over 100 countries and substantially raise testing uptake. At entry to care, the initial workup quantifies HIV RNA viral load and CD4+ T-cell count, performs genotypic resistance testing (and integrase resistance in selected regions), screens for hepatitis B, hepatitis C, syphilis, gonorrhea, chlamydia, tuberculosis (interferon-gamma release assay), and pregnancy where applicable, and assesses renal and hepatic function, lipids, glucose, and HLA-B*5701 before any abacavir-based regimen. Repeat testing every 3-6 months is recommended for people with ongoing risk; opt-out screening at least once in adulthood is recommended by USPSTF and CDC for ages 13-64.
Life expectancy for people who start antiretroviral therapy early and remain virally suppressed now approaches that of the general population. North American and European cohort studies (NA-ACCORD, ART-CC) show 20-year-olds starting ART today projected to live into their early 70s, with the gap to HIV-negative peers narrowing each year as cardiovascular and cancer screening improve. The strongest determinants of long-term outcome are time from infection to ART initiation, sustained adherence, smoking status, and management of comorbidities including hepatitis B and C, cardiovascular disease, and chronic kidney disease. Untreated HIV remains uniformly fatal: median survival from infection without ART is approximately 8-10 years in adults, with mortality rising rapidly once CD4 falls below 200 cells/µL. The most important prognostic message for newly diagnosed patients today is that with consistent therapy, HIV is a controllable chronic condition that does not shorten life span and does not pass to sexual partners or to children when treatment goals are maintained.
An infectious disease physician or HIV-experienced primary care clinician should manage initial diagnosis, regimen selection, and resistance interpretation. Specialist input is essential for treatment failure, multi-drug resistance, complex coinfections (hepatitis B or C, TB, opportunistic infections), pregnancy, pediatric HIV, post-exposure cases with source resistance, and long-acting injectable initiation. Centres of HIV expertise deliver markedly higher rates of viral suppression and lower mortality than non-experienced settings (NA-ACCORD cohort).
Find specialists →Viral load typically falls by 1-2 log within 4 weeks of starting ART and reaches below 50 copies/mL by week 12-24 in 90% of adherent patients. CD4 count rises by an average of 100-150 cells/µL during the first year of suppression, with continued slower gains over subsequent years. Opportunistic infection prophylaxis can usually be discontinued once CD4 has been above 200 cells/µL for 3-6 months on suppressive therapy. Patients with sustained suppression for 6 months meet U=U criteria for sexual non-transmission. Long-term recovery is measured in years: bone density, cardiovascular markers, and neurocognitive function improve over 2-5 years on therapy.
Aim for 150 minutes per week of moderate aerobic activity plus two sessions of resistance training. Regular exercise improves CD4 recovery, reduces visceral adiposity associated with some antiretrovirals, lowers cardiovascular risk, and improves mood. People with severe immunosuppression or active opportunistic infection should start gradually under clinical guidance. Yoga and breathwork are safe adjuncts and help with adherence to a long-term treatment routine.
Look for board certification in infectious disease or an HIV Specialist credential from the American Academy of HIV Medicine; experience with at least 25 active patients on ART; access to integrated pharmacy and case management; routine resistance testing; and explicit support for U=U counselling, PrEP, and harm reduction. In low- and middle-income settings, accredited national ART program sites and centres supported by Global Fund, PEPFAR, or Ryan White are typically the strongest options.
Medically reviewed by AIHealz Medical Editorial Board · May 12, 2026
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